


The Only Exception

by OctoberDecember



Series: #SaveShadowhunters Prompts [3]
Category: Shadowhunters (TV), The Mortal Instruments Series - Cassandra Clare
Genre: Attempt at Humor, Canon Related, Domestic Fluff, Light Angst, M/M, Magical Pregnancy, Married Magnus Bane/Alec Lightwood, Mpreg, Post Mpreg, Pregnant Magnus Bane, Unplanned Pregnancy
Language: English
Status: Completed
Published: 2018-06-17
Updated: 2018-06-17
Packaged: 2019-05-24 11:04:17
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,100
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14953469
Author URL: https://archiveofourown.org/users/OctoberDecember/pseuds/OctoberDecember
Summary: “Magnus! What happened? Are you okay?”Magnus ignored his husband’s words, as he quietly placed his hands over his own stomach…And his eyes soon went wide...As he felt a very faint trace of unfamiliar magic…Somehow coming from inside of him…Like something was…learning…how to use its powers for the first time…“No…no…no…no…no…” Magnus’ hands began to shake as the realization coldly washed over him. “No. It can’t be…it can’t…”





	The Only Exception

**Author's Note:**

  * For [sweetpandemonium](https://archiveofourown.org/users/sweetpandemonium/gifts), [Kiaris](https://archiveofourown.org/users/Kiaris/gifts).



> —I decided to take a lil angst break (y'all and these prompts WHOO Y'ALL LOVE ANGST MORE THAN I DO TBH AND THAT IS SAYING SOMETHING)
> 
> —[hang out with me on Tumblr ♥](https://octoberdecemberwrites.tumblr.com)

 

“Thank you so much, Magnus! Thank you…thank you…” The worn Shadowhunter had tears lining her eyes, as she enveloped Magnus in a rather tight embrace. “You have no idea what you’ve done…you have no idea how much you’ve changed my life…”

“My dear, it was my pleasure.” Magnus smiled, as he gently patted the Shadowhunter on her rune-filled back. “Anything for a friend of the family.”

“Yes, Alec Lightwood chose his husband well.” The Shadowhunter sniffled, as she slowly moved away from Magnus. “Please tell him how grateful I am, to the both of you.”

“I’ll make sure he knows about the sentiment.” Magnus casually wiped a tear away from the Shadowhunter’s face. “Now, go home and rest. Fertility potions are notoriously fickle. Make sure to spend the next 24 hours with your wife, as well. You’ll need to be around the one you love, for the potion to take on its full effects.”

The Shadowhunter fervently nodded, before nearly racing out of the loft.

Magnus’ expression was still stuck in a wide grin, as he thoughtfully sank into the living room couch.

_Another satisfied customer._

Magnus began to conjure up a drink or two in celebration—

Just as his loft’s doorbell loudly chimed through the room.

He snapped his fingers, letting blue sparks swirl around his fingertips—

As he opened the door to Catarina, who then happily stepped into the loft.

“Magnus Bane!” Catarina excitedly walked towards Magnus, before plopping down on the seat beside him. “I have a very, _very_ important question to ask you.”

“I think I know where you’re going with this, Catarina. And yes, while my skincare routine may be _extensive_ , if you want to have the smoothest skin in Brooklyn, you have to commit—”

“Magnus, will you be my Maid of Honor?” Catarina shouted out the question, completely interrupting Magnus’ words. “Ragnor...finally _asked_.”

Magnus was now filled with excitement, too, as he jumped away from the couch. “Catarina! That’s amazing! That’s earth-splitting! That’s as big as the vaccination for polio!”

Catarina now stood away from the couch, too, her arms wildly raised over her head. “The vaccination for polio? Magnus, this is as big as Galileo discovering that the galaxy is heliocentric!”

“Oh, it’s even much bigger than that, Catarina! Galileo’s discovery was child’s play. A warlock wedding is going to be _magnificent_.” Magnus had to stop himself from squealing with joy, as he once again called for drinks to appear in his hand—

And soon, there was a frozen, strawberry margarita in Magnus’ palm—

And one in Catarina’s, too.

“To sharing a magical future with the second most magical man in all of New York.” Magnus winked, before he tipped his glass towards Catarina’s, slightly clinking their rims.

He tipped the glass back towards his own lips—

But instead of tasting the sweet, sweet burn of his drink—

Magnus heard the very distinct sound of glass shattering against a nearby wall.

He looked down to check his hands…

Completely empty.

While his margarita glass was broken into pieces on his living room floor.

“Sorry…I just used up a lot of my magic…maybe it’s still a tad bit…off…” Magnus shrugged, as he magicked another drink into his hands—

But this one was soon smashed against the floor, too.

“Sorry…I…” Magnus shook his head in confusion, before turning to look over at his friend. “Catarina, would you mind—”

As Magnus’ gaze landed on Catarina’s, he saw a small hint of something rather unusual...

Hiding just behind her eyes…

Magnus’ breath caught in his chest once he realized the sudden, strange emotion…

_Guilt._

Catarina felt  _guilty._

He and Catarina had always been so open with each other.

He’d rarely seen her wear the expression, in all of their shared decades…

But now, she wore her guilt with abandon, as the emotion made itself plain on her face. “Magnus…I…all those years ago…”

“Catarina…What did you do?” Magnus took a step towards her, while lightly crossing his arms against his chest. “Did you…Were you trying to drain me of my magic—”

“No! No, Magnus. I would never do anything like that.” Catarina firmly shook her head, before taking in a sharp breath. “Magnus, I did…what I did…to protect you. All those years ago, when you wanted to…when you wanted to die…when you wanted to throw yourself off that bridge…I cast a spell of protection on you, Magnus. So you could never…hurt yourself again…”

Catarina winced at her admission, but she continued on with the truth. “Of course, you’re so much stronger than me, Magnus. If you really wanted to hurt yourself…you still could…but I’d be the first person to know about it…so maybe I could stop you…”

Magnus tilted his head to the side, as he tried to process her magical interference. “But Catarina, I’ve been able to drink after a long day before…I’ve been doing it for years…Why would your spell only try to stop me _now_?”

“Maybe you’re more exhausted than you realize. Maybe drinking will only aid in your exhaustion.” Catarina shrugged, before taking a small sip of her own drink. “Just give your magic some time to replete itself…”

Catarina then looked towards the ground, before speaking her next phrase. “And…I’m sorry…for using that kind of magic on you…I was just scared—”

“You don’t have to apologize for  _caring about me_ , Catarina.” Magnus offered her a bright smile, while lifting her face back towards his own. “I would’ve cast the same spell on you in a heartbeat. And maybe I already have…”

“You are the shadiest warlock I’ve ever known, Magnus Bane.” Catarina burst out into a laugh, as she sat back down on the living room couch. “Now, come on. Pitch me your ideas for my wedding’s theme. I know you’ve thought about this a million times—”

“A _billion_ times, Catarina. A billion times.” Magnus called for a book in his bedroom to appear in the palm of his hands, and soon the book was right in front of he and Catarina’s faces. “How do you feel about Paris?”

“Do you mean getting married in Paris?”

“Well, yes, except we would replicate the entire city. Maybe on a private island in the sea—”

“Magnus, that’s too much—”

“I already know someone who can make an exact duplicate of the Eiffel Tower. I’ve had his number on speed dial for twenty years—”

“Magnus!”

Catarina’s genuine laughter floated through the loft, as the old friends spent the rest of their night fawning over potential wedding plans, none of them being even  _remotely_ realistic. 

******************

Magnus impatiently watched his Shadowhunter peacefully sleep…

Time felt like it was absolutely crawling.

Magnus and Alec had made love as soon as Alec came home from work—

And Magnus very much wanted to make love to him again and again and again and again…

But, apparently, even the stamina rune had its limitations.

Magnus blew out a breath, as Alec reached an arm across Magnus’ waist.

Being intimate with Alec was nice and all, but Magnus’ skin felt like it was _on fire_. 

He needed his Shadowhunter.

Magnus whined, while nestling his face into the crook of Alec’s neck. “Alexander…”

“Hmm?” Alec sleepily responded, as his fingers lightly tapped against Magnus’ waist. “What’s wrong, Magnus?”

“I need you to perform your husbandly duties.” Magnus whined again, before playfully biting Alec on his shoulder. “Just one more time. Please, please, please. Then I promise, I’ll let you sleep for a century.”

“Fine…” Alec groaned, as he quickly sat up in their bed. “But can we at least get something to eat first? Burning through my stamina rune makes me feel like I haven’t eaten in days.”

Magnus giddily nodded, as he reached for a takeout menu on their bedside dresser. He hastily handed the menu over to Alec, while clapping his hands in rapid succession. “Go! Go! Go! Order! Order! Order! The faster it gets here, the faster I can have you.”

“Shh. Let me think.” Alec tenderly kissed Magnus’ forehead, before pulling the menu closer to his face. “I just need a few seconds, okay?”

“You’re _stalling_.” Magnus’ tone was accusatory, as he pouted over towards Alec.

“Yeah. You’re right. I am _stalling_.” Alec gently chuckled, while flipping one of the menu’s pages. “But I promise, after we eat dinner, I’ll fuck you so hard that you won’t be able to sit down tomorrow.”

Magnus rolled his eyes, before moving to lean on Alec’s bare shoulder. “I’ll be holding you to your word, Alexander.”

“Shh. Magnus. I’m trying to _read_.” Alec chuckled again, as he fully turned his attention back to the menu’s offerings.

***************

Magnus was settled onto Alec’s lap, as Alec expertly maneuvered his chopsticks around Magnus—

Picking up another piece of sushi, and deftly placing it into his waiting mouth.

“Are you hungry?” Alec’s words came out muffled between his bites. “Here. Try some.”

Magnus sighed, before opening his own mouth, wide.

The only thing he was _hungry for_ was currently in Alec’s black jeans.

But he couldn’t get to it without playing nice first…

And maybe if Magnus helped Alec finish his meal, they could retreat to the bedroom even sooner than Magnus had originally guessed.

Alec carefully placed the sushi on Magnus’ tongue—

**************

And Magnus soon found himself falling through a portal—

Landing softly on the floor of…

Ragnor Fell’s home office?

_What the hell_?

“What the hell?” Magnus repeated his thoughts, as he stood to his feet. He glanced around the room, trying to find an explanation that would satisfy him.

“Yes, what the hell, indeed.” Ragnor’s voice broke through Magnus’ confusion. “Are you here to play the considerate Big Brother, Magnus? Are you going to threaten to have me hanged if I so much as think about breaking your Catarina’s heart?”

“I wasn’t…I was…I didn’t mean to be here…” Magnus shot a nervous look over at Ragnor. “I was just…having dinner with my husband…and now I’m…here…”

Magnus took a few shaky steps towards Ragnor’s oversized, wooden desk. “Ragnor…my magic…I think I may have…done something irreparable…”

“What were you having for dinner?” Ragnor’s question came out calm, as he gave Magnus a stoic look.

“Alexander wanted sushi…”

“Sushi…” Ragnor’s voice trailed off, while he thoughtfully hummed under his breath. “And Catarina made mention of your strange inability to finish a drink without smashing it into pieces…”

“Ah! Maybe that’s it! Catarina’s spell!” Magnus gave a loud sigh of relief, as he placed a hand over his chest. “Maybe the magic has become distorted, but that would be an easy fix—”

“Old friend, I suspect that my Catarina’s spell is working perfectly fine.” Ragnor’s voice was still fairly level, as he nodded over towards Magnus. “You and your child are thoroughly secure.”

It took a few seconds for Ragnor’s words to sink in—

But once they did, Magnus let out a thunderous laugh. “Me and _my child?_ Ragnor Fell! You haven’t told a joke in 100 years, but when you finally decide to make me laugh, you excel beyond all possible expectations.”

Ragnor seemed to ignore Magnus’ laughter, as he called for a ball of glowing red energy to appear in the palm of his hand. “Now, to test the limits of Catarina’s spell…Don’t worry, dear friend. I would never truly put your child in harm’s way. But all spells must someday be tested—”

Ragnor suddenly aimed his fiery magic directly towards Magnus’ abdomen—

******************

And Magnus was once again flying through a portal—

Before landing back in Alec’s waiting lap.

“Magnus! What happened? Are you okay?”

Magnus ignored his husband’s words, as he quietly placed his hands over his own stomach…

And his eyes soon went wide...

As he felt a very faint trace of unfamiliar magic…

Somehow coming from inside of him…

Like something was…learning…how to use its powers for the first time…

“No…no…no…no…no…” Magnus’ hands began to shake as the realization coldly washed over him. “No. It can’t be…it can’t…”

“Magnus, what’s going on—”

“I made a mistake…I made a mistake…” Magnus rose from Alec’s lap, as he headed back towards their bedroom. “How could I ever make such a mistake…”

When Magnus made it to their bedroom, he hastily grabbed for his phone, dialing the number of his latest client.

With each passing second, Magnus felt his heartbeat thumping louder, pumping harder...

Magnus briefly wondered if immortal warlocks could die of a simple heart attack.

“Hello? Magnus?” The woman’s voice on the other end of the line sounded absolutely ecstatic. “It’s so wonderful to hear from you! Were you calling to check on the baby?”

“Wait…” Magnus grimaced, as he held the phone closer to his ear. “You…you’re with child? The spell succeeded?”

“Well, of course, it did, Magnus! You told me that as long as I wanted it, in my heart of hearts…and as long as my wife wanted it, too…you said it would work.” The woman gently chuckled, before taking in a shallow breath. “Why do you sound so surprised?”

Instead of answering her question, Magnus ended their conversation with the click of a button.

He then went back out into the living room, where he shot an accusatory glance over at Alec. “You…”

“Me?” Alec pointed a finger towards his own chest, while looking up at Magnus.

“You wanted a child, didn’t you?” Magnus placed his hands on his waist, before closing his eyes in frustration. “Fuck…Fuck! I was fucking doomed from the very first moment I cast that spell, wasn’t I? If I’d had known that’s what you wanted, Alexander, I never would’ve helped her! I couldn’t have helped her! It was only supposed to go one way…”

“…yes…I wanted a child…” Alec sighed after his sentence, before cautiously moving over towards Magnus. “I’ve wanted a child with you, ever since we were married last year. I just…didn’t know how to tell you, Magnus. I never knew if you wanted…I never knew if you’d ever want…”

“Well…you got exactly what you wanted, Alexander…” Magnus emphatically threw his hands into the air. “Congratulations. _We’re pregnant_.”

Alec’s eyes brightened, as he beamed back at Magnus—

“No! _How dare you_? Are you _excited_?” Magnus took a step away from Alec, pressing his back against a nearby wall. “You don’t get to be _excited_ , Alexander! This is a disaster!”

“Magnus, why would it be a disaster? You’re amazing—”

“What if they get my magic?!” Magnus looked past Alec, now yelling through his own inner fears. “My God. What if my father gets wind of it, Alexander? What if he tries to teach our child…the same, awful way he taught me…to use my magic for such evil deeds…” Magnus began to sink towards the floor, with his back slowly sliding against the wall.

“Alexander…What if they’re just like me? What if…they have my eyes?” Magnus could now feel himself nearly hyperventilating, but he couldn’t slow down his racing thoughts.

“If they’re just like you…then they’ll be beautiful…beyond beautiful…inside and out…” Alec crouched down in front of Magnus, taking Magnus’ palms into his own. “Magnus, you may not believe it right now, but this world needs _more of you_. You’re compassionate, thoughtful, genuinely kind…if our child is going to be _just like you_ , then we should thank the Angel for our luck.”

“Alexander…” Magnus’ throat closed up with emotion, as he lunged towards his Shadowhunter, pulling Alec down into his arms. “I love you…”

“I love you, too.” Alec moved his hand away from Magnus’, while delicately running his fingers along Magnus’ abdomen. “And I love _you_ , too.”

“Stop! Stop it!” Magnus groaned as he batted away Alec’s fingers. “Keep your hands to yourself, Shadowhunter.”

“But Magnus, it’s my child, too—”

“You may have added a pinch of salt to the recipe, but _I’m the one_ who has to watch the pot boil.” Magnus moved away from the wall and ran an anxious hand through his hair. “Now, if you’ll excuse me, Alexander, I need to write a fire-message to Catarina and ask her if she doesn’t mind postponing her wedding for around eight months or so…maybe nine…”

Magnus huffed and puffed, and he was soon out of the room, again—

While Alec still kept his same position near the wall, crouched on the ground—

As an uncontainable grin grew like wildfire across his face.

*****************

Magnus was dipping fresh jalapenos into generous amounts of peanut butter—

Because nothing made sense anymore.

After nine months of being pregnant, Magnus had learned to go with the flow.

And “the flow” usually consisted of increasingly bizarre food cravings, an incessant _need_ for Alec’s attention and the inability to _not_ break out into tears over the slightest of inconveniences.

Magnus heard Alec step through the front door, just as he reached for another jalapeno—

And soon, Alec peered around their bedroom with a growingly confused look. “Magnus, why are all of your clothes in the middle of the floor?”

“They’re all out of season, Alexander. I couldn’t possibly wear them outside anymore. Typically by now, I would’ve restocked my wardrobe with the latest fashions, but it’s a bit difficult getting clothes fitted with _your child_ widening my girth.”

“I hope you don’t plan on buying all new clothes, every season, for _our child_ , as well. That would be such an incredible waste—”

“Alexander! Of course, I plan on buying my child new clothes every season! The High Warlock of Brooklyn’s daughter will _not_  walk around this city in last season’s infant rompers!”

“Oh? So, when she’s causing you trouble, she’s _my child_ , but when she’s the most fashionable infant in the city, she’s _your child_?”

“Yes! Exactly! Now, you’re getting it!” Magnus took another bite out of his jalapeno—

And Alec burst out into a laugh. “You’re impossible, Magnus Bane. Utterly impossible.”

Magnus was about to ask Alec to grab him another jar of peanut butter—

When he felt a stabbing pain somewhere behind his abdomen.

He gasped for air, as he crossed his arms over his waist. “Alexander. Call Catarina. Now.”

“Magnus! Fuck! Is the baby coming? Fuck!” Alec quickly moved towards Magnus, kissing him repeatedly on his forehead. “I love you so much, Magnus. I love you, I love you—”

“Alexander! Go! Call!” Magnus pleaded, before crumpling up into a ball against their bedsheets. “The pain is too distracting. I don’t want to risk performing the magic myself. I don’t want to hurt her…”

“Okay, okay, okay…” Alec tried and failed to calm himself down, as he reached for his phone. He clumsily dialed Catarina’s number, and impatiently waited for the phone to ring.

“Alec? Is Magnus alright—”

“Come! Now! Baby! Time! Happening! Today!” Alec then swiftly hung up the phone, before moving to lie beside Magnus on their bed. “It’ll be okay, Magnus. Catarina’s coming, okay? You’ll be fine, I promise. Everything’s going to be fine…”

Magnus groaned in response, as he rolled over just enough to be in Alec’s arms. “Alexander, if I don’t survive the magic, if something happens to me—”

“ _No_.” Alec cut off Magnus’ phrase, while lightly running his hand over Magnus’ abdomen. “You’ve got me, Catarina and Marione…We would never let anything happen to you, Magnus. We love you too much to ever let you leave us.”

“That sounds like you’re holding me hostage…” Magnus slightly grinned, even though the pain was threatening to knock him unconscious.

“We _are_ holding you hostage.” Alec smiled, as he pulled Magnus tighter into their embrace. “This is for forever and always, Magnus Bane. That’s what you said at the altar. I’m holding you to that for the rest of my life.”

“I love you, Alexand—”

Magnus’ words stopped dead in their tracks—

As his entire world faded to an impenetrable black.

*****************

Magnus woke up in the middle of his living room floor.

He was drenched in colorful blankets, and his magic felt nearly impossible to detect…

He’d never felt so drained before.

Somewhere else, somewhere deep in the loft, he could hear a baby cooing…

Their noises were just high-pitched gibberish—

But every last one was like a stab to Magnus’ heart.

It hurt that he wasn’t holding his daughter, that he was in the same loft, but still somehow so far away from her…

Magnus weakly rose away from the ground, while struggling to hold out his arms.

_Fuck._

He probably wasn’t even strong enough to hold her.

Magnus’ tears stung behind his eyes, as he lied back down on the floor.

He forcefully closed his eyes, trying to will himself to just go back to bed…

Maybe when he woke up, he’d be able to hold his daughter…

But just as he was about to doze back off to sleep, he felt a weight in the very center of his chest.

He tiredly opened his eyes—

Only to see a small pair of hazel eyes staring right back at him.

As the small face peered further into Magnus’ own, he noticed a replica of Alec’s familiar deflect rune already appearing on his daughter’s neck…

“Little one, how did you…” Magnus’ tone was lined with bewilderment, as he softly ran his fingers along the rune. “Shadowhunters are not born with these…Are they?”

Marione softly whispered another round of childish gibberish, before she tightly closed her eyes—

When she opened them again, her eyes were now a golden yellow.

She giggled to herself, and unsteadily pointed a finger towards Magnus’ eyes, too.

“Glamours…already…” Magnus beamed at Marione, as he softly patted her arms. “Oh, little one. You’re going to take over the world, aren’t you?”

Alec came rushing into the living room, his breathing ragged and uneven. “There you are, Marione! I turn around for one second, and you fly out of the room—”

“ _Fly_?” Magnus looked back at his daughter…

He glanced over her jet-black, slightly curly hair…

Her naturally sun-kissed skin…

And a pair of iridescent wings, protruding directly from her spine…

“She has… _wings_?” Magnus’ jaw fell open in surprise. “Are those from _you_ or from _me_?”

Alec shrugged, as he reached down to grab Marione.

Once he had her in his arms, she giggled again, before she licked Alec right down the middle of his face, for absolutely no reason at all…

“You don’t respect me at all, do you?” Alec muttered with wonder, as Marione went in for another round of inexplicable licking. “I’m the head of the New York Institute…”

“Sorry, Alexander. If she’s anything like me, she’s not really going to respect…anyone, until she’s, oh, I don’t know…104 years old? Maybe 105? At least that’s when I really started to respect my elders.” Magnus added his commentary from the floor, as he stared up at Alec.

And Alec smiled down at Magnus, before cautiously getting into position beside his husband on the floor.

Alec then held Marione to his chest, as she began to conspicuously yawn.

“We should probably get some rest, too, Magnus…Catarina said something about sleeping when the baby sleeps?” Alec turned towards Magnus, planting a soft kiss on his cheek. “And I’ll take first shift when she wakes up, so you can have more time to recover.”

“First shift? Are you going to raise our child as if she’s a mission?”

“She _is_ a mission, Magnus. And the mission is to raise a fearless, ambitious, woman of the world…”

“So, we’re basically raising Isabelle Lightwood 2.0?”

“Yeah, but _better_ because she’s part _you_.”

“Mmhmm. As soon as I get my strength back, I’m going to tell Izzy you said that…” Magnus chuckled under his breath, as he closed his eyes for a second time. “Thank you, Alexander…”

“What are you thanking me for, Magnus? You literally did all of the work…”

“Thank you…for wanting this…for wanting her…for wanting me…” Magnus’ voice became lower and lower, as he began to drift off into sleep. “Thank you for making us…a family…”

As Magnus finally slipped off into his dreams, Alec quietly rearranged the blankets surrounding them, making sure each member of the Lightwood family was sufficiently covered with warmth…

Alec then silently kissed his warlock on the forehead—

And then he kissed his somehow-already-rebellious infant daughter’s forehead, too—

Before Alec settled back onto the floor and dozed off with an impossibly warm glow somewhere behind his chest.

**Author's Note:**

> spoilers:
> 
> —[click here to #SaveShadowhunters](https://saveshadowhunters.com)
> 
> —fun fact: this was my first mpreg prompt and I legit had no idea what I was doing but uhhhh here we are 
> 
> —Marione is 100% a work of pure fiction based on nothing except my own imagination (it's not canon, it's not even close)
> 
> —I lowkey just wanna' write about Alec + Magnus as dads now???? this fic was such a nice break from my typical angst omg WHO KNEW WRITING ABOUT FATHERHOOD WOULD BE SUCH A RELIEF FROM ANGST HAPPY FATHER'S DAY YOU GUYS MARIONE WILL BE GETTING ALEC A HEADACHE FOR FATHER'S DAY BECAUSE SHE'S TINY AND GREAT <3 
> 
> —[P.S. yes I am running out of fic titles (my fic naming abilities are G O N E) so yes another song title is here](https://www.youtube.com/watch?v=ChXcD6Z4uvQ)


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